Do driers come with moisture in them?

I never thought about this before but since I've started doing 410A systems
I'm using a lot more driers.I've noticed that it takes considerably longer
to get to 500 microns on systems with new driers installed than those with
none at all. We virtually never use driers on R22 new installations & get
to 500 microns usually in twenty minutes where it can take hours on 410A
installations where a drier is used. So far the drier is the only common
denominator I've found that changes with the installations along with the
time it takes to pull down. 
 Anyone else notice a difference.